Abstract: Objective：To study the changes of transforming growth factor-1(TGF-1) and tumor necrosis factor-(TNF-) in serum at different stages in the development of rat silicosis model.Methods：Thirty healthy male SD rats were randomly divided into silica exposure group(20 rats) and control group(10 rats).Silica suspension at 40 mg/ml(1 ml) was administrated intratracheally once while equal amount of saline was intratracheal instilled to the rats in control group.Animals were sacrificed at 1st,7th,14th,21th and 28th day after instillation.The levels of TGF-1 and TNF- in serum were determined by ELISA.Results：In contrast to control group,TGF-1 level was decreased at 1st and 7th day(P〈0.01),and increased at 14th,21th and 28th day(P〈0.01) in experiment group.And TNF-level was increased at 1st,7th,and 14th day(P〈0.01),and decreased at 21th and 28th day(P〈0.01).Conclusions：Silica can induce the changes of serum TGF-1 and TNF- in experimental silicotic rat model.The unusual high expression of TGF-1 might take part in the pulmonary fibrosis.